Process for promoting the emulsion polymerization of conjugated diolefins



atente Jan. I, 194

PROCESS FOR PROMOTDIG THE E I SIGN lggg%lgRIZATION F GONJUGATED DI- Anthony H. Gleason,

Sparks, signments, to tion of Louisiana Elizabeth, N.

and whom a.

3., assignors, by me as- Jasco, Incorporated, a corpora- No Drawing. Application September 19, 1941,

Serial No.

8 Claims. (01. zoo-sis) or in an interpolymerization reaction with other polymerizable substances such as styrene or its homologs, the acrylonitriles, the unsaturated ketones, the acrylate esters and similar unsaturates, by preparing them in the form of an aqueous dispersion or emulsion in water, maintained by the presence of emulsifying agents and polymerized by the, presence of oxygen liberating compounds. Attempts have been made to promote and accelerate the polymerization reaction and to obtain more plastic products by the presence in the polymerization mixture of halogenated compounds such as-carbon tetrachloride; also various organic compounds such as xanthogen polysulfldes, thioacids, mercapto compounds,'and various nitro and amino compounds have been LISE'A'I as promoters.

The present invention provides a new and useful promoter in the form of carbon disulfide as an addition agent to the polymerization mixture. The efi'ect of the carbon disulfide is to increase the speed of the polymerization reaction. The carbon disulfide is particularly advantageous because of its low cost. The promoting and plasticizing eifect also can be markedly influenced by utilizing carbon disulflde in combination with the previously used mercaptans and halides to give.-

a still more satisfactory reaction rate and improved plasticity in the product.

An object of the present invention is to increase rthe rate of polymerization of a. diolefin or of a mixtureoi a diolefln with another polymerizable organic compound; and to improve the placticity of the resulting polymer; a further object is to promote the polymerization reaction by the presence of an inexpensive promoter in the form of carbon disulfide, either alone or in admixture with other promoters; and to polymerize the unsaturated materials into polymers having the desired property of good plasticity and capable of reacting with sulfur to give vulcanranging from 4 or 5 hours to 'edly to. permit izates of good tensileand of high resilience; and, in addition, to polymerize mono-oleflnic material such as styrene or its homologs while in emulsion form. Other objects and details of the invention will be apparent from the following description.

In the priorart it has been customary to polymerize the olefins particularly the diolefins such as butadiene, either alone or 'in admixture, with other oleflnic material or other unsaturates, by preparing a. mixture of the unsaturates in convenient proportions, usually either the diolefln alone or the diolefin with another unsaturate in which the diolefin is present in the proportion of more than 40 to 50%. 1 The oleflnic material is then emulsified in water with the aid of an appropriate soap or other emulsifier such as sodium 1 stearate, sodium isopropyl napthalene sulfonate, cation active emulsifiers and the like, either singly or in various mixtures. The polymerization catalyst usually takes the form of an oxygen providing substance, preferably a peroxide such as hydrogen peroxide or sodium perborate or potassium persuliate or the like. This mixture is then preferably maintained at a temperature between 25 C. and about C. for a time interval 25 to 3o hours; preferably not more than about 20 hours, while the polymerization reaction occurs. When a sumcient yield has been obtained, usually from 65 to 85% v of the original content of unsaturates, the emul-v sion is freed from part or all of the monomers, and the emulsion coagulated by the application. of a suitable coagulant such as a brine solution. The coagulate is then washed, dried, and compounded with various substances and vulcanized.

In practicing the present invention a substantial proportion of carbon disulflde is added to the polymeriation mixture and retained in the mixture during the polymerizing reaction. The carbon disulfide is removed, in part at least, with the unpolymerized unsaturates in the emulsion at the end of the polymerization period. The

presence oi the carbon disulfide is found to increase the speed of polymerization very-markof the carrying of the reaction to a much higher otherwise possible. Also, the presence of the carbon disulfide increases the plasticity of the finished polymer. The carbon disulflde is partic-- ularly eflective in the polymerization of a diolefin such as butadiene, either alone or in admixfl ture with such unsaturates such as styrene, acryl onitrile, ethyl. cinnamate, methacrylic esters,

iumarie esters, vinyl ketones and the like. The desirable amount of carbon disulfide present in the reaction mixture may range from 0.5% to 01' the amount of oleflnic reactants. A deyield in a shorter time than is sirable olefin for use in connection with this promoter may be found in butadiene or isoprene or piperylene; or dlmethyl butadiene or other polyolefins which are capable oi 'polymeriatlon or of interpolymerization with other polymerizable substances.

Exmets 1 Fifteen parts-oi butadiene and 5.6 parts of in combination, to modify the properties oithe copolymer to yield both a more rapid rate of poly merization and to yield a more plastic polymerizate capable of easy working on a rubber mill.

- that instead of using 15 cc. of carbon disulflde a similar quantity of carbon tetrachloride was polymerization reaction for mixtures of butadiene with acrylonitrile in the presence of various concentratlons of carbon disulflde, both in the absence of mercapto-type compounds and in the presence of mercapto-type compounds such as benzyl mercaptan, as shown. In all these examples the same emulsifier and catalysts were employed, as in Example 1. These examples show that carbon disulflde is an effective polymerization promoter for the preparation of rubbet-like materials of the Buna" type.

These experiments have also shown that carbon disuliide is effective with b'enzyl mercaptan,

acrylonitrile were emulsified in 45 parts of water, substituted therefor. The yield of the resulting having dissolved therein 5 parts of a 2.8 solution polymer was 26% in 16 hours. This quantity of of potassium persultate and approximately 1.2 carbon tetrachloride results in a low yield, which parts of sodium oleate. To this mixture there is apparently due to the dilution effect. The was added 1 part ofgcarbon disulfide. The emulsame dilution is present when carbon disulflde sion of these various materials was maintained in is employed but owing to itsv strong promoting a pressure vessel by rapid stirring over a time action the yield is not diminished but somewhat interval of 16 hours, and the temperature was increased. I held at 35 C. At the end of this time interval, The reaction is not limited to butadiene-acryia latex-like emulsion was obtained. This emulonitrile mixtures, but is equally applicable to sion was coagulated by the addition of approxi- 30 other known combinations for preparing synmately an equal volume of saturated brine. The thetic rubber such as butadiene-styrene and isogresulting coagulum amounted to 81% of the origprene-styrene.

inal unsaturates. The coagulum was washed Examples 9 and 10, conducted like Example 1, with water and dried by milling on a warm roll show, the improvement obtainable by the presmill to yield an elastic. somewhat plastic mate ence of carbon disulfide in the interpolymerizarial, which when compounded with sulfur and tion of styrene and isoprene.

' Table II Example iifl" ttitifii" dttlilt News tits. ass

the usual compounding ingredients'vulcanized 'The promoting eflect is similarly effective in into a good, resilient, rubber-like substance. the presence of octyl mercaptans, as is shown in Similar experiments, #2 to 7 inclusive, were Examples 11 and 12 in Table III.

Table III R tan o taut, 0 b0 m bats. art"... was W in. a: arr

Gram Grams 11 15.0 5.6 None 0.1cc. octyl -35 3 i2 15.0 6.6 0.26 .do 20 39-35 51 conducted in the same way, with varying propor- These examples show that the polymerization tions of the various constituents, as shown in Tareaction of a diolefin alone or the interpolymerble 1. ization reaction of a diolefin with another poly- Table l' assault, 0 mam, 0 b0 Tim, 'r butadicne fil yloniti'lla an ina Mempm hour atti Gram Grams mo 6.6 16 4o 0 no as 11 to 15.0 as ---.do 11 40 92 16.0 5.0 O.4ec.benzyl.- 1 11 4o 25 ran as dc 11 40 55 15.0 at 15.000 .do 1e 40 81 These examples show the promotion of the merizable organic compound, as above pointed out, can be markedly speeded up and promoted trations as little as 0.01% to as high as about 4.0%

to impart to the interpolymer the desiredplasticity and other properties suitable for milling to give desirable yields of the polymerizate while spears The relative quantities referred to, the additions and methods for shooting the same, as well as the temperatures of polymerization can be varied within wide its. It will be re understood, that the invention is not restricted by the above examples whichare only intended to show how the invention can be carried into effect. instead of e: r a diolednic compound or mixtures thereof, various cohinatlons such as a diolefinic compound with an alkyl substituted styrene or homologs thereof with an un saturated ester such as dodecycl methacrylate, polymerizable esters of clnnamic, iumarlo, acrylic merizates of technically valuable properties rang ing from plastic, elastic materials to hard, tough and thermoplastic resins, depeng, oi course, upon the concentration of reactant or reactants; which can he variedawithin wide f it l of an oxygen providing poerization catalyst and an emulsifier, the improvement which consists of promoting the polymerization reaction by the addition of a member of the group consisting of carbon disulfide, mixtures of carbondisulflde with benzyl mercaptan and mixtures of carbon disulphide with octyl mercaptan, the amount of carbon disuifide present r ng from 0.5 to 75% of the amount of the unsaturated organic reactants.

3. In the process oiproducing emulsion polymerizates which consists oi emulsifying in fer a mixture of butadiene with a styrene in the pres ence of an oxygen providing poerisatlon catalyst and an emulsifier, the improvement which consists ofproinoting the poetion reac [tion by the addition of a member of the group acids. etc., can he copolerised to give poly- The present invention, therefore, provides a 7 method for prooting the polymerization reaction or a nioiennic compound with other polyrncrlzable compounds by which stable colors or resins are formed rapidly in one step in a high yield without the need of enercis control over the proportionsoi the promoter used. It will further he seen that the process presents an in. provement over previous inventions in this field.

While there are above disclosed but a limited number of embodiments of the invention, it is possible to produce still other embodiments with-' out departing from the inventive concept herein disclosed, and it is therefore desired that only such item. he imposed upon the appended claims as are stated therein or required by the prior art.

The invention claimed is:

1. In the process of producing emulsion polymerizates which consists of emulsifying in water an unsaturated organic compound selected from the group consisting of conjugated aliphatic diolefin hydrocarbons and mixtures oi conjugated aliphatic diolefin'hydrocarbons with compounds copolymerizable with said conjugated dioleflns under the conditions of the reaction containing a single C=C linkage per molecule in the presence of an oxygen providing polymerization catalyst and an emulsifier, the improvement which consists of promoting the polymerization reaction by the addition of a member. of the group consisting of carbon disulfide, mixtures of carbon disulfide with benzyl mercaptan and mixtures of carbon disulphide with-octyl mercaptan.

2. In the process of producing emulsion polymerizates which consists of emulsifying in water an unsaturated organic compound selected from the group consisting oi conjugated aliphatic diolefin hydrocarbons and mixtures of conjugated aliphatic diolefihhydrocarbons with compounds carbon disulphide with octyl mercapm merizates which consists of emulsii .i-i

consisting of carbon 'discle, xtures of carbon disulfide with'benzyl mercapta'n and mixtures of amount of carbon disde present ranging from 0.5 to 75% of the amount of the butadiene and V the styrene in the reaction mixture. 4. In the process of producing emulsion polymerizates which consists of emulsifying in watera mixture of isoprene with a styrene in the presence of an oxygen providing hoerinatlon catalyst and an emulsifier, the improvement which consists of promoting the tion reaction by the addition oi a member of the group consisting of carbon disulfide, mixtures oi carbon disulfide with henzyl mercaptan and urea of carbon disulphide with octyl mercaptan, the

amount of carbon disulfide present ranging from 0.5 to 75% of the amount of the isoprene and the styrene in the reaction mixture.

5. In the process of prucing emon polyg in water a mixture oi butadiene with acrylonitrile in the presence of an oxygen providing polymerization catalyst and an emulsifier, the improvement which consists of promoting the polerization reaction by the adtion of a member of the group copolymerizable with said conjugated diolefins consisting oi carbon disulfiide, stores of carbon disuliide with benzyl merceptan and mixtures of carbon disulphide with octyl mcrcapten, the

amount of carbon dlsulfide present rains from 0.5 to of the amount of the hutediene and acrylonitrile in the reaction mixture.

6. In the process oi producing emulsion polymeriaates which consists of emulsifying in water an unsaturated organic compound selected from the group consisting of conjugated aliphatic diolefin hydrocarns and mixtures oi conjugated aliphatic diole hydrocarbons with compounds copolymerizable with said conjugated dioleflns under the conditions of the reaction containing a single (2:0 linkage mr molecule in the presence oi an oxygen providing polerization catalyst and an emulsifier, the improvement which consists of promoting the polymerization reaction by the addition of from 0.5 to 75% of the amount of the unsaturated organic reactants or carbon disuliide.

7, In the process of producing emulsion polythev aliphatic diolefin hydrocarbons with compounds 10 copolymerizable with said conjugated dioleflns under the conditions of the-reaction containing a. single C=C linkage per molecule in the presence of an oxygen providing polymerization catalyst and an emulsifier, the improvement which consists of promoting the polymerization reaction by the addition of from 0.5 to 15% of the amount of the unsaturated organic reactants of carbon disulfide and octyl mercaptan,

ANTHONY H; GLEASON. WILIJAM ,J. SPARKS. 

